You asked
Leica summarit m 35mm f 2 4 asph vs zeiss biogon t 35mm f 2 zm?
Both are 35mm primes for full frame Leica M cameras, and both are manual focus with no stabilisation. They fit the same bodies, so the choice comes down to the lens itself.
The Zeiss Biogon T* 35mm f/2 ZM is the faster of the two. f/2 lets in more light than f/2.4, which helps in dim interiors and gives a little more background separation. If you shoot in low light or want that extra room, I'd pick this one.
The Leica Summarit-M 35mm f/2.4 ASPH is from Leica's discontinued, lower-priced Summarit line. If you want a 35mm for a Leica M and don't need the wider aperture, it's the more economical route into the system.
Both are for the Leica M mount, so check that your body takes it before you buy.
Written by Claude from this site's pages.